1. Field of the Invention
The present invention relates to redundant cable systems for operating closures and, more specifically, to devices for indicating the failure of one of the cables.
2. Description of the Prior Art
Closures, such as windows or doors, may be suspended from double chains or cables. Conventionally, one cable is attached to each side of the closure. Weights may be attached to the other end of the cables to equalize the strain of the closure. If one of the cables fails, by breaking or becoming disconnected, the closure will stand ajar and may itself become disconnected and fall.
In a redundant cable system, both cables are connected to one side of the closure. The load is reduced by half and the life of the cables is increased. The closure is generally supported in a track or similar device. When one of the cables does fail, the closure does not become ajar. There is little noticeable difference in the operation of the closure. Continued operation, however, places a double stress on the intact cable and poses a risk of injury to the operator who is unaware of the weakened state of the closure suspension mechanism.
There is a need for a device which indicates the failure of one of the cables in a redundant cable system for use with closures which will not place stress on the intact cable. There is a further need for such a device which is safe to operate.